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conjoined twins are twins (usually female) are twins that share same body parts, some even have the same brain and two different bodys!

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https://www.youtube.com/watch?v=B1J6Ou4q8vE
My friend showed me this video
It shows everything about math in less than a few years =P
I barely understand some of the things in this...

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Try MY GAME and Studio(for all my games .^.)!

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Try MY GAME and Studio(for all my games .^.)!

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https://scratch.mit.edu/projects/829501190/
https://scratch.mit.edu/studios/33654390/

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So today I went for SST written paper thing, and I manage to answer all questions but one, and it's really bothering me. Can anyone help to answer?

So there is person A and person B. They are both 5km apart and facing each other. Person A travels towards person B at 20km/h while person B travels towards person A at 30km/h. When they meet, they turn around and travel back to their starting point. When they reach their starting points, they turn around again and continue until they meet. This repeats. How far will person B have traveled when they meet for the fifth time?

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Kingfisher Helps Reshape Bullet Trains | Bullet trains in Japan used to make a loud boom sound when they traveled through tunnels. A bird-watching engineer was able to fix the problem after he... | By Interesting Engineering | Facebook

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2.2M views, 11K likes, 1.7K loves, 155 comments, 3.1K shares, Facebook Watch Videos from Interesting Engineering: Bullet trains in Japan used to make a loud boom sound when they traveled through...

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What Is Eutrophication | Agriculture | Biology | FuseSchool

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What does three degrees of global warming look like? | The Economist

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Climate change: Earth's giant game of Tetris - Joss Fong

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Climate crisis: Where will it be too hot to live? - BBC Newsnight

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The Speed, Distance and Time trick [No Ads]

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SPEED COMPARISON 3D | Fastest Man Made Objects

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Additional for the below gear ratio video

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Additional for the below gear ratio video

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NEVER be confused by GEAR RATIOS again - EXPLAINED in the MOST VISUAL WAY using LEGO

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How to find 1 interior angle only knowing how many sides is the regular polygon?

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Create a customized Pie Chart for free. Enter any data, customize the chart’s colors, fonts and other details, then download it or easily share it with a shortened url | Meta-Chart.com !

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Despite often being maligned, the pie chart remains a very commonly-seen chart type. In this article, you will learn how to best use this frequently-misused chart type.

What is a pie chart?

A pie chart shows how a total amount is divided between levels of a categorical variable as a circle divided into radial slices. Each categorical value corresponds with a single slice of the circle, and the size of each slice (both in area and arc length) indicates what proportion of the whole each category level takes.

The pie chart above depicts the distribution of votes for a fictional election for a small city. We can see that Reyes, represented by the first blue slice, has just less than half of the votes. Chu (yellow) is in second, with about a third of the votes, while Williams (purple) is last, with about a fifth of the votes. The annotations in the upper right give us a more precise judgment of the proportions, but the pie chart tells the overarching story of where the votes fell.

When you should use a pie chart

Pie charts have a fairly narrow use-case that is encapsulated particularly well by its definition. In order to use a pie chart, you must have some kind of whole amount that is divided into a number of distinct parts. Your primary objective in a pie chart should be to compare each group's contribution to the whole, as opposed to comparing groups to each other. If the above points are not satisfied, the pie chart is not appropriate, and a different plot type should be used instead.

The values that comprise a whole and the categories that divide the whole generally come in two major varieties. First of all, is when the 'whole' represents a total count. Examples of this include votes in an election divided by candidate, or number of transactions divided by user type (e.g. guest, new user, existing user).

A second type of 'whole' is when the total is a sum over an actual data variable. For example, we might be interested not in the number of transactions, but the monetary total from all transactions. Dividing this total by an attribute like user type, age bracket, or location might provide insights as to where the business is most successful.

Example of data structure

Data for a pie chart can be summarized in a table like the above, where the first column indicates a category, and the second the proportion, frequency, or amount of that category. Usually, the total does not need to be specified separately unless it is to be listed somewhere else on a generated figure. Alternatively, some tools can just work with the unaggregated data as in the below table, essentially performing the aggregation into the table above at time of pie chart creation.

Best practices for using a pie chart

Include annotations

It is actually very difficult to discern exact proportions from pie charts, outside of small fractions like 1/2 (50%), 1/3 (33%), and 1/4 (25%). Furthermore, if the slice values are meant to depict amounts rather than proportions, pie charts typically lack the tick marks to allow for estimation of values directly from slice sizes. It is for these reasons that annotations are a standard inclusion for pie charts.

Consider the order of slices

A good order for slices can make it much easier for a reader to understand what the plot is saying. A typical ordering goes from the largest slice to the smallest slice, very useful when there are categories with very similar values. However, if the category levels have an inherent ordering, then plotting slices in that order is usually better.

As for choosing a start point, it's a good idea to plot slices from a cardinally-oriented direction. Visualization tools will usually start from the right or from the top. While starting from the right has a mathematical basis regarding conventions on measuring angles, starting from the top feels more intuitive, since it matches how we read from top to bottom, and how we think about progression of time on a clock or watch face.

We do not sort by size here since the labels are meaningful.

Limit the number of pie slices

Pie charts with a large number of slices can be difficult to read. It can be difficult to see the smallest slices, and it can be difficult to choose enough colors to make all of the slices distinct. Recommendations vary, but if you have more than about five categories, you might want to think about using a different chart type. As another option, you might consider lumping small slices into a single 'other' slice, colored in a neutral gray.

Avoid distorting effects

Reading a pie chart accurately requires that the slices' areas, arc lengths, and angles all point to an accurate representation of the data. While avoiding 3-d effects is a good idea for any plot, it is especially important for pie charts. Squashing or stretching the circle or adding unnecessary depth can easily distort how large each slice compares to the whole.

Another distortion can come from the 'exploded' pie chart, where slices are pulled out from the center for emphasis. This emphasis comes with a cost, where the gaps can make it more difficult to actually gauge the part-to-whole comparison.

Common misuses

Fitting a pie to incompatible data

One of the most common mistakes with using a pie chart is to fit it to data that does not represent a parts-to-whole comparison. This confusion occurs most often when the values to be plotted are percentages or proportions, but don't comprise a complete whole. The example below shows how frequently the people surveyed used each of four applications, but since many people used multiple apps, the proportions sum to much more than 100%.

Another tricky case is if the values used for each group are a summary statistic that is not a total. The chart below was built on the average transaction amount for multiple transaction types. However, since it ignores how frequently each transaction type was used, it distorts how much revenue is coming in from each type. While checks have the highest average, they might also be fairly rare in use. In both cases, a bar chart is an appropriate chart type to use.

Using pie charts to compare groups to one another

If you want to make comparisons between groups rather than from each group to the whole, then you are better off with a different chart type. Even when sorting slices by size, it can be difficult to tell how different two slices are, especially when they move away from the start / end point. In the below example, you might assume that the second slice is larger than the third due to order, but the corresponding bar chart actually shows the opposite. The main thing that you can really say from the pie chart is that both slices are approximately the same proportions from the whole.

Comparing values across multiple pie charts

There may be cases where you will want to compare multiple pies to one another: for example, comparing user demographic distribution across multiple years. However, this runs into a similar issue as the previous section, where you want to compare groups to one another. Even worse, it's a comparison between pies, so you can't rely on the order of slices as easily for the comparison. Expressing the data using a different plot, like stacked bar chart, grouped bar chart, or line chart, is often a better choice when this kind of group-to-group comparison is desired. Like with actual pies, pie charts are best taken one at a time.

Comparison of the pies may imply a shrinking of the older age groups by proportion, but the grouped bar chart demonstrates a growth in the younger groups.

Common pie chart options

Absolute frequency vs. relative frequency

Pie charts can be labeled in terms of absolute values or by proportions. Labeling slices with absolute amounts and implying the proportions with the slice sizes is conventional, but consider the goals of your visualization carefully in order to decide on the best annotation style to use for your plot. In some cases, including both numbers in the annotations can be worth the additional text.

Doughnut plot

A doughnut plot (aka donut plot) is simply a pie chart with a central circle removed. For the most part, there aren't significant differences in readability between a pie chart and donut chart, so the choice of a doughnut over a standard circle is mostly that of aesthetic. One small boon for the ring shape is that the central area can be used for additional information or to report statistics.

The biggest competition for the pie chart comes from the bar chart. Most of the time, you won't want to use a pie chart - rather, a bar chart will get across the points more compactly and clearly. Many of the issues with pie charts are solved through the use of a bar chart. However, bar charts do not immediately sell the part-to-whole comparison, which is pie chart's major benefit.

On the other hand, the stacked bar chart type can prove to be a strong rival to the pie chart in its ability to communicate a part-to-whole comparison. A single stacked bar can be thought of as a pie chart's slices rolled out into a rectangular form. The rectangular form also makes it easier to compare categorical breakdowns across different groups. However, pie charts still have an advantage in familiarity and aesthetics, so they're still worth having in mind for the part-to-whole comparison use case.

Waffle chart

Another alternative to the pie chart is the waffle chart, also known as a square chart or square pie. A waffle chart comprises 100 icons, typically squares laid out in a 10 x 10 grid. Each icon represents 1% of the data, and the icons are colored based on the categorical distribution of the data. While there will need to be some rounding of category amounts to fit the plot structure - never split icons in this plot - it can be a way of making the relative proportions for each category easier to read.

Visualization tools

Most visualization tools will be able to create pie charts, despite their limited use case. Donut charts are somewhat less common, but there aren't a whole lot of cases where they're truly needed over pie charts. Despite the fact that pie charts have fallen out of favor for most visualization needs, it is important to recognize that they are a common chart that people generally know how to read. Pie charts are still great at their ideal job: immediately selling a part-to-whole comparison objective.

The pie chart is one of many different chart types that can be used for visualizing data. Learn more from our articles on essential chart types, how to choose a type of data visualization, or by browsing the full collection of articles in the charts category.

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Despite often being maligned, the pie chart remains a very commonly-seen chart type. In this article, you will learn how to best use this frequently-misused chart type. A pie chart shows how a total amount is divided between levels of a categorical variable as a circle divided into radial slices.

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Volume of Pyramid - Formula, Derivation, Definition, Examples

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The volume of a pyramid refers to the space enclosed between its faces. The volume of a pyramid whose base area is ‘B’ and whose height is ‘h’ is V = (1/3) Bh.

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Varsity Tutors connects you to top tutors through its award-winning live learning platform for private in-home or online tutoring in your area.

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Includes info beyond P6 PSLE syllabus

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A circle is a curved plane figure. Every point on the circle is equidistant from a fixed point known as the center of the circle. It is a 2D shape and is measured in terms of radius. The word ‘Circle’ is derived from the Latin word 'circulus' meaning small ring.

What is Circle?

A circle is a two-dimensional figure formed by a set of points that are at a constant or at a fixed distance (radius) from a fixed point (center) on the plane. The fixed point is called the origin or center of the circle and the fixed distance of the points from the origin is called the radius.

Parts of a Circle

There are many parts or components of a circle that we should know to understand its properties. A circle has mainly the following parts:

Circumference: It is also referred to as the perimeter of a circle and can be defined as the distance around the boundary of the circle.

Radius of Circle: Radius is the distance from the center of a circle to any point on its boundary. A circle has many radii as it is the distance from the center and touches the boundary of the circle at various points.

Diameter: A diameter is a straight line passing through the center that connects two points on the boundary of the circle. We should note that there can be multiple diameters in the circle, but they should:

pass through the center.

be straight lines.

touch the boundary of the circle at two distinct points which lie opposite to each other.

Chord of a Circle: A chord is any line segment touching the circle at two different points on its boundary. The longest chord in a circle is its diameter which passes through the center and divides it into two equal parts.

Tangent: A tangent is a line that touches the circle at a unique point and lies outside the circle.

Secant: A line that intersects two points on an arc/circumference of a circle is called the secant.

Arc of a Circle: An arc of a circle is referred to as a curve, that is a part or portion of its circumference.

Segment in a Circle: The area enclosed by the chord and the corresponding arc in a circle is called a segment. There are two types of segments - minor segment, and major segment.

Sector of a Cirlce: The sector of a circle is defined as the area enclosed by two radii and the corresponding arc in a circle. There are two types of sectors - minor sector, and major sector.

For better understanding observe the given image depicting all parts of a circle.

Properties of Circle

Let us move ahead and learn about some interesting properties of circles that make them different from other geometric shapes. Here is a list of properties of a circle:

A circle is a closed 2D shape that is not a polygon. It has one curved face.

Two circles can be called congruent if they have the same radius.

Equal chords are always equidistant from the center of the circle.

The perpendicular bisector of a chord passes through the center of the circle.

When two circles intersect, the line connecting the intersecting points will be perpendicular to the line connecting their center points.

Tangents drawn at the endpoints of the diameter are parallel to each other.

Circle Formulas

Let's see the list of important formulae pertaining to any circle.

Area of a Circle Formula: The area of a circle refers to the amount of space covered by the circle. It totally depends on the length of its radius → Area = πr² square units.

Circumference of a Circle Formula: The circumference is the total length of the boundary of a circle → Circumference = 2πr units.

Arc Length Formula: An arc is a section (part) of the circumference. Length of an arc = θ × r. Here, θ is in radians.

Area of a Sector Formula: If a sector makes an angle θ (measured in radians) at the center, then the area of the sector of a circle = (θ × r²) ÷ 2. Here, θ is in radians.

Length of Chord Formula: It can be calculated if the angle made by the chord at the center and the value of radius is known. Length of chord = 2 r sin(θ/2). Here, θ is in radians.

Area of Segment Formula: The segment of a circle is the region formed by the chord and the corresponding arc covered by the segment. The area of a segment = r²(θ − sinθ) ÷ 2. Here, θ is in radians.

Related Topics

Check these interesting articles related to circles in math.

Constructing Circles

Circumference of Circle Calculator

Equation of Circle Calculator

Symmetry of Any Circle

Chords and Diameters

FAQs on Circles

What is a Circle in Geometry?

A circle is a round 2-dimensional shape. It is a closed shape with a distance from center to circumference termed as radius 'r' and distance from one point on the circumference to another point passing through center termed as diameter 'd'. One of the best examples of the circle in the real world is a pizza base.

How Circle is Two-Dimensional?

A circle is a closed two-dimensional figure in which the set of all the points in the plane is at the same distance from the center of the circle. Its real-life examples include flat surfaces or pictures of wheels, pizzas, orbit, etc.

What are the Formulas of Circles?

Formulas related to circles are:

Diameter of a Circle ⇒ D = 2 × r units.

Circumference ⇒ C = 2 × π × r units.

Area ⇒ A = π × r² square units.

What is a Half-Circle called in Geometry?

In geometry, a semicircle refers to the half of a circle. The diameter divides the circle into two equal parts that are semi-circles.

What is a Chord in a Circle?

A chord is the line segment joining two points inside a circle on its arc. As the diameter also having two endpoints on a circle, so, it is the longest chord. All angles marked in the circle subtended by the same chord are equal.

What are the Major Parts of a Circle?

The list of the different parts of a circle includes tangent, chord, radius, diameter, minor arc, major arc, minor segment, major segment, minor sector, and major sector.

What is the Circumference of a Circle?

The circumference of a circle is defined as the linear distance around its boundary or we can say, if a circle is opened to form a straight line, then the length of that line will be the circle's circumference.

What are the Properties of Circles?

Following are some of the properties of circles:

The two circles with equal radius are congruent in nature.

The diameter is the longest chord of a circle and it divides the circle into two equal parts.

The radius of the circle bisects the chord if it is drawn perpendicular to the chord.

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Circles - Properties, Formulas, Parts, Examples

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A circle is a curved plane figure. Every point on the circle is equidistant from a particular point, the point is called the center of the circle. Learn about circles with concepts, properties, and examples.

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New year, new school, new opportunities for growth! Read our article as we share some tried and true tips for parents and children in the lead up to the first day of primary school.

A Whole New World Awaits

New classmates, new teachers, new school environment - your child's tiny world is about to get a lot bigger. With these changes come opportunities for personal, social and cognitive growth.

The Countdown And Preparation Begins

In these weeks as you count down to your child's first day of school, you may be wondering, "What will school be like for my child? Will my child be able to cope in the new environment?"

Parents can help by being proactive - research from professionals at Duke University suggests that establishing a strong communication channel with your child's teachers helps and so does monitoring changes in your child's behaviour or mood when he or she first starts school.

Whether at home or in school, we've got some great tips for every stage of preparation that will help you (and your child) pave a smooth journey towards the new school term in January.
1. Create A Routine That Works
Studies have shown that routines help children feel safe and secure. Set up a routine that works for your child - whether it's a shower before dinner or an afternoon snack before naptime, it's important that your child gets into a routine that he or she is comfortable with.
2. Identify Friendly Figures In School
Helping your child identify teachers or staff he or she can go to for assistance is important. When your child recognises trustworthy figures of authority, he or she will feel more secure in the new environment.
Related Article: Gear Up For Primary 1 3. Prepare An 'Emergency' Fund
You may want to consider setting aside an "emergency fund" for your child. Placing extra money in a separate wallet or purse to be kept in his or her school bag means that your child will still have access to money if he or she misplaces pocket money. However, you should set some strict rules about when this money can be used.
4. Test Out That Transport Route
It may be a good idea to have a few dry runs of your child's journey to and from school to help your child familiarise himself or herself with the route. Help your child identify key landmarks and remember the specific place where he or she will be dropped off or picked up from everyday.
Related Article: Raising A Responsible Child 5. Set Mini Goals To Achieve Together
Help to make the experience seem less daunting by setting mini goals for the first day of school. Start with small tasks like "Leave the house on time" or "Remember to bring my water bottle home" or "Meet one new friend in class today". These mini goals give your child something to look forward to on his or her first day of school!

Download Our Special Guide To Surviving And Thriving In Primary 1

The Learning Lab would like to extend our help as you and your child are preparing for Primary 1 and the new adventures that lie ahead. Download our fun and informative guide filled with 25 great tips to help your child survive and thrive in Primary 1!

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3 Ways to Solve the Challenging 2019 PSLE Maths Circle Question

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New year, new school, new opportunities for growth! Read our article as we share some tried and true tips for parents and children in the lead up to the first day of primary school. New classmates, new teachers, new school environment - your child's tiny world is about to get a lot bigger.

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Carnivorous UNDERCOVER caterpillar 🐛😎 | Wild Isles - BBC

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Pallas Cats
Honduran White Bats
Siberian Flying Squirrels
Highland Cattle
Red Pandas
Western Pygmy Possum
Sugar Gliders
Bush Babies
Sea Bunny
Dumbo Octopus

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Loosely related to adaptations

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The Nature of Monster Hunter - Variants | Ecology Documentary

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We've focused on Predator-Prey relationships in Primary 6.

There are other relationships such as Mutualism, Commensalism and Parasitism.

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Transcript

Hi, and welcome to this video on mutualism, commensalism, and parasitism!

Have you ever noticed any interactions between organisms in nature that you thought were especially interesting? Like bees pollinating flowers or clownfish living in sea anemones? Symbiotic relationships like these are all around you if you know where to look. Organisms can use such a relationship to benefit from one another in several ways, such as transportation, food, shelter, growth, and reproduction, just to name a few.

Mutalism

So if we take the two examples we just mentioned, the bees pollinating the flowers and the clownfish living in sea anemones, we have two classic examples of how organisms can mutually benefit from one another so that both organisms can thrive. When both organisms in a symbiotic relationship benefit, we call this mutualism. In the case of the bees and the flowers, bees need pollen to make honey which they use as a food source, so the bees go from flower to flower gathering pollen which they store in a pouch in their abdomen or on their hind legs depending on the species. When the bees move on from one flower to the next, some of the pollen brushes off and pollinates the new flower. Both the bees and the flowers benefit from this relationship, so it's a good example of mutualism. Clownfish and sea anemones have the same sort of mutualistic relationship. To other fish, brushing up against a sea anemone is deadly. But clownfish are unaffected by the anemone's sting because they have adapted to form a protective mucous on their skin. So the clownfish is able to live in the sea anemone and in the process keeps it clean, while the sea anemone gives the clownfish protection and a place to live.

Another example of mutualism that you may not have thought of is the symbiotic relationship between, us, humans, and the bacteria in our gut. Take lactobacillus bacteria for a specific example. Lactobacilli are a common type of bacteria found in yogurt, cheese, and some plants. So when you eat any of these foods, the bacteria will make a home out of your intestines by feeding off of the sugars you eat while simultaneously helping you digest that sugar. Both parties benefit, so this is also a mutualistic relationship.

Commensalism

Commensalism is another type of symbiotic relationship where one organism benefits and the other organism isn't benefited or harmed either way. Golden jackals will follow tigers on their hunt for prey so that they can feed off of the tiger's scraps. The tiger does all of the work to actually catch and kill its prey, but it doesn't seem to mind the jackal cleaning up after it. Since the jackal benefits and the tiger isn't affected, we can say that this is an example of commensalism.

Commensalism Examples

Another example of commensalism is one organism using another as a means of transportation. A lot of insects, fish, and other animals use each other in this way, but a good example is the remora. This is a type of suckerfish that will attach itself to sharks and other big fish to catch an underwater ride. This in and of itself is an example of commensalism since only the remora really benefits, but this relationship can change to mutualism when the remora feed on the parasites on the backs of these big fish. This leads us to our last type of relationship, which is parasitism.

Parasitism

Parasitism is a type of relationship where one organism benefits and the other organism is harmed in some way.

Parasitism Examples

Your mind might jump to what we more commonly think of as a parasite like tapeworms or fleas. These are great examples because in both cases, the parasite benefits while the other organism is harmed. As humans, we can get tapeworms from the food and water we consume if it is not treated or prepared properly. Once the tapeworm is inside of the digestive tract, it eats a lot of your food for you. So symptoms can range from increased appetite to nausea, but if the tapeworm spreads to other organs it can be life-threatening. However, parasitic relationships aren't limited to the microscopic or small-scale world. Cowbirds are a species of birds that instead of raising their own young, take advantage of another bird species, since birds cannot easily distinguish between their young. Female cowbirds will lay their eggs in another bird's nest, like a black-capped chickadee, and the female black-capped chickadee will feed both her own young and the cowbird nestling. However, cowbirds are much larger than most birds so they will demand more of the food and nest space. In the end, this means some of the black-capped chickadee's young will die while the cowbird nestling lives.

So, to review, mutualism is where both organisms benefit, commensalism is where one benefits and the other is unaffected, and parasitism is where one benefits and the other is harmed.

Review

Before we go, here's a review question:

Which is the best example of mutualism?

1. A flea and a dog

2. A squid and an anglerfish

3. Cattle and crows

4. A poison dart frog and a cricket

Show Answer

Thanks for watching, and happy studying!

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Examples of Mutualism, Commensalism, and Parasitism (Video)

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Transcript Hi, and welcome to this video on mutualism, commensalism, and parasitism! Have you ever noticed any interactions between organisms in nature that you thought were especially interesting? Like bees pollinating flowers or clownfish living in sea anemones? Symbiotic relationships like these are all around you if you know where to look.

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Thanks for correcting me! Higher altitude = lower pressure :)

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Sambar deer making a return in Singapore, study shows

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The deer likely recolonised parts of the forests here after escaping from enclosures in the 1970s. Read more at straitstimes.com.

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Dead trees like this are a key resource in the forest, providing valuable roosting and nesting sites for a range of birds and mammals.

Over the years, several trees like the one on the left have fallen over. We have left these large trunks on the ground, allowing them to decay in situ.

The decomposition of a fallen tree is a wonderful example of recycling.

The molecules that were taken from the soil and air during the hundred plus years of growth of a large eucalypt like this are returned to the environment.

There they will support the growth of new trees and many other organisms.

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A rotten log - ecosystem in miniature - Life in a Southern Forest

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Dead trees like this are a key resource in the forest, providing valuable roosting and nesting sites for a range of birds and mammals. Over the years, several trees like the one on the left have fallen over. We have left these large trunks on the ground, allowing them to decay in situ.

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Key Concepts
Biodiversity
Biology
Soil
Invertebrates

Introduction
Do you enjoy walking through piles of autumn leaves and hearing the crunch underneath your feet? Those leaves you're stepping on might actually be home to a wide variety of plants and animals! Leaves, twigs and pieces of bark that have fallen to the ground make up leaf litter. Leaf litter is an important component of healthy soil. Decomposing leaf litter releases nutrients into the soil and also keeps it moist. It also serves as great nesting material, hiding places and protected spots for animals. This dead organic material provides the perfect habitat for a plethora of organisms, including worms, snails, spiders, and microscopic decomposers like fungi and bacteria. For this reason, leaf litter is considered very biodiverse.

"Biodiversity" is a concept that refers to the variety of different life forms, from the genetic level to the species level. Species diversity in particular is a subcategory of biodiversity that refers to the number of different species represented in a set. Where can biodiversity be seen in your everyday life? Just look outside your window! The different types of trees, flowers and insects are all examples of a biodiverse community.

Scientists use various mathematical formulas and indices to calculate biodiversity. The level of biodiversity in an ecosystem is believed to indicate how healthy and stable the ecosystem is. Generally, a higher biodiversity level indicates a healthy ecosystem that is capable of supporting life well. To learn more about biodiversity, you can examine leaf litter in your neighborhood!

Background
Most of the tiny animals that are found in leaf litter are invertebrates, meaning that they lack a backbone. Some of these little critters feed on the litter and break it up into smaller pieces. Microscopic organisms like bacteria and fungi then decompose the litter, converting it into beneficial chemicals and minerals that can be absorbed by plants.

Animals you may find living in leaf litter include slugs and snails, worms, animals with jointed legs (like millipedes and centipedes), spiders and beetles. The type and amount of organisms found varies with time of year. Some animals spend their entire lives in soil and leaf litter, while others are found there only at certain points in their lives. Some use the litter specifically for nesting or hibernating.

In this activity, you will be able to see the biodiversity levels of leaf litter in your neighborhood and how human activity has impacted these levels.

Materials
* A partner
* A trowel or short shovel
* Gloves (gardening gloves or winter gloves will do)
* One large tray (aluminum trays work well)
* One small tray
* Two magnifying glasses
* Tweezers
* Meter stick
* Rope
* Pencil and paper
* Field guide or identification key (optional)

Preparation
* Locate a nearby public park or forest to conduct the activity. Acquire a map of the area.
* The best time to conduct this activity is in the autumn months.

Procedure
* Travel to a nearby park or public forest. Locate an area that has been relatively undisturbed by human activity. There should be many fallen leaves, twigs and pieces of bark. Remember to have a partner with you at all times.
* Once you've found a suitable patch of leaf litter, measure out an area of one meter squared using the meter stick. Use the rope to build a rough frame. This will serve as a one-meter vegetation sampling frame. Have you seen any animals in your sampling area so far? How many types of animals do you think you will find?
* With the vegetation sampling frame on the ground, put on your gloves and use the trowel to collect all the leaf layer and soil within the frame (down to a depth of approximately two centimeters (cm) from the surface).
* Place all the leaf litter in the large tray. Using your fingers but keeping your gloves on, spread out the leaf litter so an even layer is created. Keep your eye out for little critters!
* With your magnifying glasses, you and your partner should examine the leaf litter for any worms, snails, spiders or other insects. Use your gloved fingers to gently sift through the litter.
* Using tweezers, gently place any animals found in the litter into the smaller tray. You should find specimens like snails, worms and spiders. Don't worry if you can't get all the insects.
* Using the magnifying glasses, examine the small animals. How many legs are there, if any? Do they have an external skeleton or a hard shell? Do their legs appear to be jointed? Scientists use questions like these to categorize animals into different groups.
* Look out for obvious differences like color, size, and shape to distinguish species. Record the number of different species you can see. If you see many different species, there is a high biodiversity. If there are only a few species present, there is a low biodiversity.
* Return all specimens and leaf litter material to where you originally found them. Disassemble your rope frame. Make sure you do not leave anything that you brought behind!
* Travel to another location with leaf litter. However, this time find an area that has more human interference. These are areas that people frequently use - places like walking and hiking trails.
* Reassemble the vegetation sampling frame and place on the ground.
* As with the previous location, gather the leaf litter and soil within the sampling frame (down to approximately two cm deep). With your gloved fingers, sort the leaf litter in the large tray. Transfer any specimens found into the smaller tray and examine them under the magnifying glass.
* Count and record the number of species you see in this set. If you see many different species, there is a high biodiversity. If there are only a few species present, there is a low biodiversity.
* Return all specimens and leaf litter material to where you originally found them. Again, make sure you do not leave anything you brought with you behind!
* Which area had the higher biodiversity level - the one with little human interference or the one with much more? What types of animals did you find? Remember that organisms like fungi and bacteria also live in leaf litter, and these organisms cannot be seen without a microscope.
* Extra: Instead of just counting the number of species, you can identify them like a real research scientist would! Using a dichotomous key like the ones listed in the "More to explore" section, you can narrow down your specimen to the family, genus or species level!

Observations and results
Did the leaf litter found in an area with lots of human interference have a lower biodiversity?

In recent years, there has been a significant loss in biodiversity, caused primarily by human activity. Such biodiversity loss usually occurs on a large scale, and is due to habitat destruction, invasive species, overexploitation and climate change. In the areas with lots of human interference, human activity has contributed to a lower biodiversity. People might litter on the ground or simply step on animals. Other times, people may add chemical fertilizers and pesticides to the soil. These activities all contribute to a loss of biodiversity. A low biodiversity is unfavorable because these ecosystems take longer to recover from environmental changes.

On the other hand, the first sampling site with little human activity should have had a higher biodiversity level. A higher biodiversity level means that site has a more stable ecosystem. High biodiversity is also important because it supports many ecological processes. For instance, a high biodiversity of decomposers and small insects is important in regulating soil chemistry, recycling nutrients and providing fertile soils.

More to explore
Hope College Leaf Litter Arthropod Key from Hope College
Life in the Leaf Litter ( pdf- English, pdf- Spanish) from the American Museum of Natural History
Scientists Spend 10 Years Watching Leaf Litter Decay for Clues to Climate Change from Scientific American
Spiders in Borneo: Spiders in leaf litter from Scientific American

This activity brought to you in partnership with CityScience

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Seasonal Science: What Lurks in the Leaf Litter?

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Key Concepts Biodiversity Biology Soil Invertebrates Introduction Do you enjoy walking through piles of autumn leaves and hearing the crunch underneath your feet? Those leaves you're stepping on might actually be home to a wide variety of plants and animals! Leaves, twigs and pieces of bark that have fallen to the ground make up leaf litter.

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According to the what's up newspaper, the nuclear fusion lazers produce 1.5times the energy used for the lazers itself. Where does the extra energy come from?

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This is a "behavioural adaptation"

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How Does Huddling Help Penguins Stay Warm? | BBC Earth

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Does angle ABC = 90 degrees or 270 degrees?

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Secondary 1/ IP 1 Mathematics: Percentage Change

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How Trees Accomplish the Impossible | How Trees Accomplish the Impossible | By Veritasium | Facebook

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1.4M views, 16K likes, 3K loves, 830 comments, 9.9K shares, Facebook Watch Videos from Veritasium: How Trees Accomplish the Impossible

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Meet 'Leaf Sheep,' The Photosynthesizing Sea Slugs - Childhood By Nature

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'Leaf sheep' is a bizarre kind of sea slug that is biologically named 'Costasiella Kuroshimae.' It is the only organism in the entire world that is not a plant yet is able to photosynthesize. This sheep is also able to produce enough energy through kleptoplasty that helps them stay alive for at least 2 months...

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I might have it

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Centers for Disease Control and Prevention

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ADHD is one of the most common neurodevelopmental disorders of childhood. It is usually first diagnosed in childhood and often lasts into adulthood. Children with ADHD may have trouble paying attention, controlling impulsive behaviors (may act without thinking about what the result will be), or be overly active.

Signs and Symptoms

It is normal for children to have trouble focusing and behaving at one time or another. However, children with ADHD do not just grow out of these behaviors. The symptoms continue, can be severe, and can cause difficulty at school, at home, or with friends.

A child with ADHD might:

daydream a lot

forget or lose things a lot

squirm or fidget

talk too much

make careless mistakes or take unnecessary risks

have a hard time resisting temptation

have trouble taking turns

have difficulty getting along with others

Learn more about signs and symptoms
Types

There are three different ways ADHD presents itself, depending on which types of symptoms are strongest in the individual:

Predominantly Inattentive Presentation: It is hard for the individual to organize or finish a task, to pay attention to details, or to follow instructions or conversations. The person is easily distracted or forgets details of daily routines.

Predominantly Hyperactive-Impulsive Presentation: The person fidgets and talks a lot. It is hard to sit still for long (e.g., for a meal or while doing homework). Smaller children may run, jump or climb constantly. The individual feels restless and has trouble with impulsivity. Someone who is impulsive may interrupt others a lot, grab things from people, or speak at inappropriate times. It is hard for the person to wait their turn or listen to directions. A person with impulsiveness may have more accidents and injuries than others.

Combined Presentation: Symptoms of the above two types are equally present in the person.

Because symptoms can change over time, the presentation may change over time as well.

Causes of ADHD

Scientists are studying cause(s) and risk factors in an effort to find better ways to manage and reduce the chances of a person having ADHD. The cause(s) and risk factors for ADHD are unknown, but current research shows that genetics plays an important role. Recent studies link genetic factors with ADHD.

In addition to genetics, scientists are studying other possible causes and risk factors including:

Brain injury

Exposure to environmental risks (e.g., lead) during pregnancy or at a young age

Alcohol and tobacco use during pregnancy

Premature delivery

Low birth weight

Research does not support the popularly held views that ADHD is caused by eating too much sugar, watching too much television, parenting, or social and environmental factors such as poverty or family chaos. Of course, many things, including these, might make symptoms worse, especially in certain people. But the evidence is not strong enough to conclude that they are the main causes of ADHD.

Diagnosis

Deciding if a child has ADHD is a process with several steps. There is no single test to diagnose ADHD, and many other problems, like anxiety, depression, sleep problems, and certain types of learning disabilities, can have similar symptoms. One step of the process involves having a medical exam, including hearing and vision tests, to rule out other problems with symptoms like ADHD. Diagnosing ADHD usually includes a checklist for rating ADHD symptoms and taking a history of the child from parents, teachers, and sometimes, the child.
Learn more about the criteria for diagnosing ADHD
Treatments

In most cases, ADHD is best treated with a combination of behavior therapy and medication. For preschool-aged children (4-5 years of age) with ADHD, behavior therapy, particularly training for parents, is recommended as the first line of treatment before medication is tried. What works best can depend on the child and family. Good treatment plans will include close monitoring, follow-ups, and making changes, if needed, along the way.
Learn more about treatments
Managing Symptoms: Staying Healthy

Being healthy is important for all children and can be especially important for children with ADHD. In addition to behavioral therapy and medication, having a healthy lifestyle can make it easier for your child to deal with ADHD symptoms. Here are some healthy behaviors that may help:

Get Help!

If you or your doctor has concerns about ADHD, you can take your child to a specialist such as a child psychologist, child psychiatrist, or developmental pediatrician, or you can contact your local early intervention agency (for children under 3) or public school (for children 3 and older).

The Centers for Disease Control and Prevention (CDC) funds the National Resource Center on ADHD, a program of CHADD - Children and Adults with Attention-Deficit/Hyperactivity Disorder. Their website has links to information for people with ADHD and their families. The National Resource Center operates a call center (1-866-200-8098) with trained staff to answer questions about ADHD.

For more information on services for children with special needs, visit the Center for Parent Information and Resources. To find the Parent Center near you, you can visit this website.

ADHD in Adults

ADHD can last into adulthood. Some adults have ADHD but have never been diagnosed. The symptoms can cause difficulty at work, at home, or with relationships. Symptoms may look different at older ages, for example, hyperactivity may appear as extreme restlessness. Symptoms can become more severe when the demands of adulthood increase. For more information about diagnosis and treatment throughout the lifespan, please visit the websites of the National Resource Center on ADHD and the National Institutes of Mental Health.

More Information

Reference

Faraone, S. V., Banaschewski, T., Coghill, D., Zheng, Y., Biederman, J., Bellgrove, M. A., . . . Wang, Y. (2021). The World Federation of ADHD International Consensus Statement: 208 evidence-based conclusions about the disorder. Neuroscience & Biobehavioral Reviews. doi:10.1016/j.neubiorev.2021.01.022

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ADHD is one of the most common neurobehavioral disorders of childhood. It is usually first diagnosed in childhood and often lasts into adulthood. Children with ADHD have trouble paying attention, controlling impulsive behaviors (may act without thinking about what the result will be), and in some cases, are overly active.

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gravity bombs

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Free body diagrams, we will learn this in Sec school

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Free body diagrams, we will learn this in Sec school

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Free-body diagrams are diagrams used to show the relative magnitude and direction of all forces acting upon an object in a given situation. A free-body diagram is a special example of the vector diagrams that were discussed in an earlier unit. These diagrams will be used throughout our study of physics. The size of the arrow in a free-body diagram reflects the magnitude of the force. The direction of the arrow shows the direction that the force is acting. Each force arrow in the diagram is labeled to indicate the exact type of force. It is generally customary in a free-body diagram to represent the object by a box and to draw the force arrow from the center of the box outward in the direction that the force is acting. An example of a free-body diagram is shown at the right.

The free-body diagram above depicts four forces acting upon the object. Objects do not necessarily always have four forces acting upon them. There will be cases in which the number of forces depicted by a free-body diagram will be one, two, or three. There is no hard and fast rule about the number of forces that must be drawn in a free-body diagram. The only rule for drawing free-body diagrams is to depict all the forces that exist for that object in the given situation. Thus, to construct free-body diagrams, it is extremely important to know the various types of forces. If given a description of a physical situation, begin by using your understanding of the force types to identify which forces are present. Then determine the direction in which each force is acting. Finally, draw a box and add arrows for each existing force in the appropriate direction; label each force arrow according to its type. If necessary, refer to the list of forces and their description in order to understand the various force types and their appropriate symbols.

We Would Like to Suggest ...

Sometimes it isn't enough to just read about it. You have to interact with it! And that's exactly what you do when you use one of The Physics Classroom's Interactives. We would like to suggest that you combine the reading of this page with the use of our Free-Body Diagram Interactive. You can find it in the Physics Interactives section of our website. The Free-Body Diagram Interactive allows a learner to practice identifying the forces that act upon an object and to express such an understanding by the construction of a free-body diagram.

Practice

Apply the method described in the paragraph above to construct free-body diagrams for the various situations described below. Answers are shown and explained at the bottom of this page.

1. A book is at rest on a tabletop. Diagram the forces acting on the book. See answer.

2. A gymnast holding onto a bar, is suspended motionless in mid-air. The bar is supported by two ropes that attach to the ceiling. Diagram the forces acting on the combination of gymnast and bar. See answer.

3. An egg is free-falling from a nest in a tree. Neglect air resistance. Diagram the forces acting on the egg as it is falling. See answer.

4. A flying squirrel is gliding (no wing flaps) from a tree to the ground at constant velocity. Consider air resistance. Diagram the forces acting on the squirrel. See answer.

5. A rightward force is applied to a book in order to move it across a desk with a rightward acceleration. Consider frictional forces. Neglect air resistance. Diagram the forces acting on the book. See answer.

6. A rightward force is applied to a book in order to move it across a desk at constant velocity. Consider frictional forces. Neglect air resistance. Diagram the forces acting on the book. See answer.

7. A college student rests a backpack upon his shoulder. The pack is suspended motionless by one strap from one shoulder. Diagram the vertical forces acting on the backpack. See answer.

8. A skydiver is descending with a constant velocity. Consider air resistance. Diagram the forces acting upon the skydiver. See answer.

9. A force is applied to the right to drag a sled across loosely packed snow with a rightward acceleration. Neglect air resistance. Diagram the forces acting upon the sled. See answer.

10. A football is moving upwards towards its peak after having been booted by the punter. Neglect air resistance. Diagram the forces acting upon the football as it rises upward towards its peak. See answer.

11. A car is coasting to the right and slowing down. Neglect air resistance. Diagram the forces acting upon the car. See answer.

Answers

Answers to the above exercise are shown here. If you have difficulty drawing free-body diagrams, then you ought to be concerned. Continue to review the the list of forces and their description and this page in order to gain a comfort with constructing free-body diagrams.

1. A book is at rest on a tabletop. A free-body diagram for this situation looks like this:

2. A gymnast holding onto a bar, is suspended motionless in mid-air. The bar is supported by two ropes that attach to the ceiling. Diagram the forces acting on the combination of gymnast and bar. A free-body diagram for this situation looks like this:

3. An egg is free-falling from a nest in a tree. Neglect air resistance. A free-body diagram for this situation looks like this:

4. A flying squirrel is gliding (no wing flaps) from a tree to the ground at constant velocity. Consider air resistance. A free-body diagram for this situation looks like this:

5. A rightward force is applied to a book in order to move it across a desk with a rightward acceleration. Consider frictional forces. Neglect air resistance. A free-body diagram for this situation looks like this:

6. A rightward force is applied to a book in order to move it across a desk at constant velocity. Consider frictional forces. Neglect air resistance. A free-body diagram for this situation looks like this:

7. A college student rests a backpack upon his shoulder. The pack is suspended motionless by one strap from one shoulder. A free-body diagram for this situation looks like this:

8. A skydiver is descending with a constant velocity. Consider air resistance. A free-body diagram for this situation looks like this:

9. A force is applied to the right to drag a sled across loosely packed snow with a rightward acceleration. Neglect air resistance. A free-body diagram for this situation looks like this:

10. A football is moving upwards towards its peak after having been booted by the punter. Neglect air resistance. A free-body diagram for this situation looks like this:

Return to Questions Return to Info on Free-body diagrams Return to on-line Force Description List

11. A car is coasting to the right and slowing down. Neglect air resistance. A free-body diagram for this situation looks like this:

Return to Questions Return to Info on Free-body diagrams
Return to on-line Force Description List

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Free-body diagrams are diagrams used to show the relative magnitude and direction of all forces acting upon an object in a given situation. A free-body diagram is a special example of the vector diagrams that were discussed in an earlier unit. These diagrams will be used throughout our study of physics.

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this is about friction

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Friction | Hot Wheels Labs | @Hot Wheels

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10 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 (100zeros):1       gear ratio!

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To celebrate being alive for a billion seconds, Daniel Bruin built a machine with 100 gears with a 10-to-1 gear ratio...meaning that the overall gear ratio is a googol-to-one. (A googol is 1 with 100 zeros.)

This machine has a gear reduction of 1 to 10 a hundred times. In order to get the last gear to turn once you'll need to spin the first one a google [sic] amount around. Or better said you'll need more energy than the entire known universe has to do that. That boggles my mind.

You can watch the machine spin for an hour - it's kinda relaxing:

Bruin says his machine was inspired by Arthur Ganson's Machine with Concrete, a contraption whose gears spin so slowly that the final gear is embedded in concrete. (via digg)

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Here's What a Googol-to-One Gear Ratio Looks Like

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To celebrate being alive for a billion seconds, Daniel Bruin built a machine with 100 gears with a 10-to-1 gear ratio...meaning that the overall gear ratio is a googol-to-one. (A googol is 1 with 100 zeros.) This machine has a gear reduction of 1 to 10 a hundred times.

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yes

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How Hackers Hide Themselves Using the Dark Web

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Mysterious Places That Could Be PORTALS To Other Worlds

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really

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The Formula 1 Car with INFINITE GEARS | The Blueprint

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I have had this in my house for at least 4 years and only now I wonder how it works

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Onion prices have more than quadrupled since late 2022, and the vegetable is now more expensive than meat. In December, onion prices rose as high as 700 pesos (S$17) per kg, double the cost of beef and pork at wet markets.

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An omelette of a crisis: Why onion, egg prices are rising in Philippines

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As the Philippines weathers a shortage in more food staples, critics are pushing President Ferdinand Marcos Jr to finally appoint an agricultural secretary. Read more at straitstimes.com.

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A zygote is the fertilised egg cell that results from a sperm fertilising an egg, and contains all the genetic information from both parents to form a baby. The zygote soon starts to divide and subdivide into many more cells called blastomeres, which eventually form the embryo.When a zygote splits into two and each zygote goes on to develop into an embryo, this leads to identical twins. If it divides into three, triplets are formed, Science Daily reported.

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A zygote is the fertilised egg cell that results from a sperm fertilising an egg, and contains all the genetic information from both parents to form a baby. The zygote soon starts to divide and subdivide into many more cells called blastomeres, which eventually form the embryo.When a zygote splits into two and each zygote goes on to develop into an embryo, this leads to identical twins. If it divides into three, triplets are formed, Science Daily reported.

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From twins to triplets, celebrating CNY with their triple bundles of joy

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The chances of an embryo splitting into triplets are "extremely rare". Read more at straitstimes.com.

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The role of the wind tunnel in Formula One

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https://www.youtube.com/watch?v=3KqjRPV9_PY&ab_channel=WIRED

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Aerodynamics Explained by a World Record Paper Airplane Designer | Level Up | WIRED

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this is why cars can make a full loop-de-loop without falling.

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basically a speculation of what may happen if the earth had perfect conditions for frogs to diversify and evolve.

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'Amphiterra' Explained | Speculative Biology

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Theme Park Rides That Had To Be Shut Down - Part 2

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What has four wheels and flies? ( a garbage truck )

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https://www.youtube.com/watch?v=nKKjItiSBDQ (video on how the forces work)

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The lift force, lifting force or simply lift is the sum of all the forces on a body that force it to move perpendicular to the direction of flow.

The most common type of lift is that of a wing of an aircraft. But there are many other common uses such as propellers on both aircraft and boats, rotors on helicopters, fan blades, sails on sailboats, and wind turbines.

While the common meaning of the term " lift" suggests an "upwards" action, lift can be in any direction. For instance, for a sail the lift is horizontal, and for the wing on a race car the lift is down.

There are a number of ways of explaining the production of lift; some are more complicated than others, some have been shown to be false. The simplest explanation is that the wing deflects air downward, and the reaction pushes the wing up.

Other websites

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The lift force, lifting force or simply lift is the sum of all the forces on a body that force it to move perpendicular to the direction of flow. The most common type of lift is that of a wing of an aircraft.

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Astronauts float around in space because of microgravity.

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So you know the sls package on forces right? Section B part 1 Qn 1 it asks you 'Which of the following is an effect of a force'
The last option is 'A force can cause an object to increase in temperature' which can be true. Because you can use friction to create heat.
And a shadow is formed when an object blocks light or stops light from reaching where the shadow is so the 5th option may also be correct.
And for the 7th option I'm just thinking of a balloon, like when you blow it up with air it has more mass(I think)

so yeah

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This is the wrong chapter so I am waiting for the miscellaneous section to exist

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This is the wrong chapter so I am waiting for the miscellaneous section to exist

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https://www.vedantu.com/evs/non-flowering-plants

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Non-Flowering Plant

The plants which do not produce flowers are known as non-flowering plants. Various examples of non-flowering plants such as hornworts, liverworts, and Pinus fall under this category. These plants usually reproduce with or through spores. Here we will discuss the definition of non-flowering plants , how non-flowering plants reproduce , and the different types of non-flowering plants that are there in the world.

What is a Non-Flowering Plant?

Plants that do not produce flowers are classified as non-flowering plants. Bryophytes, pteridophytes, and gymnosperms are some examples. Gymnosperms generate seeds, however, they are not contained within the ovary. The ovule and pollen grains develop within the sporangia found on microsporophylls and megasporophylls, which spirally organise to create male and female strobili or cones. Flowering plants, angiosperms, have male and female reproductive systems in their flowers.

Types of Non-Flowering Plants

There are assorted types of categories which come under the types and are explained as follows:

1. Spores Producing Non-Flowering Plants

Such types of non-flowering plants reproduce by releasing large numbers of tiny spores.

Seeds are not produced by them and they use spores. Furthermore, Spores are tiny organisms that contain single cells. Also, Spores are too tiny and light that they can be dispersed by wind to assorted locations, and further where they reach they Grow there themselves.

These are soft and spongy. This type of Non-flowering plant can only grow a few inches tall. And they prefer to Grow in Clumps or we can say they grow in Cushions. Mosses don't have flowers or seeds, But they utilise the Spores to Reproduce. Apart From this Mosses plants attach themselves to rocks in the soil with Short Growths known as Rhizoids.

Another type of Non-flowering plant is Known as Ferns. They also produce spores and look Like brown colour spots and are also dust like in nature. Ferns are found underneath the leaves. When mature the Spores explode and substances are released that further come in contact with soil and reproduction initiates.

2. Seeds Producing Non-Flowering Plants

The seeds are released by the cones and are Winged in nature. They Float on the wind. They float until they reach the ground, where they Germinate and Grow further. They are called Gymnosperms.

Gymnosperms

Gymnosperms are also called Naked seeds because their seeds are open to the air without any Covering and are kind of naked which makes the name so. They have no flowers or Fruits. One of the major Groups of this category is Conifers.

Conifers mean bearing Cones. They use cones to store seeds. These are woody Plants and include trees such as Pine Trees, firs, cedars, and Redwoods.

This type reproduces using cones and is also known as Conifers. They can be Male cones or female cones. The ones which are male cones release pollen and if pollen lands on a female cone, It produces Seeds. Pollen is carried away by the wind.

Do All Plants Have Seeds?

We can say that not all plants do not bear seeds. There are numerous ways in which plants Reproduce. But here as we are talking about Non-flowering plants, so we can say that all plants do not have seeds. Liverworts and hornworts are also without seeds. Numerous plants do not possess Seeds. Plants such as Ferns, and Mosses which are Non-flowering In nature produce spores instead of seeds. Also, mushrooms are produced by spores.

How do Non-Flowering Plants Reproduce?

We can say that non-flowering plants reproduce by spore formation. In this process, large numbers of tiny spores are released. Spores are produced in a structure called sporangia. Sporangia is a structure within which spores are produced. These can be single cells or can be multicellular. Unlike seeds, spores are usually single reproductive cells in nature.

Interesting Facts about Non-Flowering Plants

There are over 12,000 Assorted species of Mosses.

Most Trees are non-flowering plants. The leaves of the trees are very vital.

The Largest non Flowering plant is Redwoods.

Pines are Non-flowering evergreen plants. They remain Green throughout all seasons hence called evergreen.

Leaves of ferns are called Fronds. Ferns are some of the oldest plants found Millions of years ago

Non Flowering plants mainly fall into one of the above-mentioned groups such as Ferns, liverworts, mosses, cones, and Gymnosperm. Gymnosperms are a good source of food. Also, they are a good source of starch. Various species of Non-flowering plants are also used in the Production of Wine Some algae also fall under non-flowering Plants.

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Non-Flowering Plant The plants which do not produce flowers are known as non-flowering plants. Various examples of non-flowering plants such as hornworts, liverworts, and Pinus fall under this category. These plants usually reproduce with or through spores.

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We are learning about Law of Conservation of Energy now - "energy can neither be created nor destroyed, but can be converted from one form to another"

We are really just skimming the surface. In Sec sch and beyond, you will learn about how this is true only for isolated systems etc.

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Introduction

What kind of system are you: open or closed? As it turns out, this is a physics question, not a philosophical one. You, like all living things, are an open system, meaning that you exchange both matter and energy with your environment. For instance, you take in chemical energy in the form of food, and do work on your surroundings in the form of moving, talking, walking, and breathing.

All of the exchanges of energy that take place inside of you (such as your many metabolic reactions), and between you and your surroundings, can be described by the same laws of physics as energy exchanges between hot and cold objects, or gas molecules, or anything else you might find in a physics textbook. Here, we'll look at two physical laws - the First and Second Laws of Thermodynamics - and see how they apply to biological systems like you.

Systems and surroundings

Thermodynamics in biology refers to the study of energy transfers that occur in molecules or collections of molecules. When we are discussing thermodynamics, the particular item or collection of items that we're interested in (which could be something as small as a cell, or as large as an ecosystem) is called the system, while everything that's not included in the system we've defined is called the surroundings.

For instance, if you were heating a pot of water on the stove, the system might include the stove, pot, and water, while the surroundings would be everything else: the rest of the kitchen, house, neighborhood, country, planet, galaxy, and universe. The decision of what to define as the system is arbitrary (up to the observer), and depending on what you wanted to study, you could equally well make just the water, or the entire house, part of the system. The system and the surroundings together make up the universe.

There are three types of systems in thermodynamics: open, closed, and isolated.

An open system can exchange both energy and matter with its surroundings. The stovetop example would be an open system, because heat and water vapor can be lost to the air.

A closed system, on the other hand, can exchange only energy with its surroundings, not matter. If we put a very tightly fitting lid on the pot from the previous example, it would approximate a closed system.

An isolated system is one that cannot exchange either matter or energy with its surroundings. A perfect isolated system is hard to come by, but an insulated drink cooler with a lid is conceptually similar to a true isolated system. The items inside can exchange energy with each other, which is why the drinks get cold and the ice melts a little, but they exchange very little energy (heat) with the outside environment.

You, like other organisms, are an open system. Whether you think about it or not, you are constantly exchanging energy and matter with your surroundings. For instance, suppose that you eat a carrot, or lift a bag of laundry onto a table, or simply breathe out and release carbon dioxide into the atmosphere. In each case, you are exchanging energy and matter with your environment.

Exchanges of energy that take place in living creatures must follow the laws of physics. In this regard, they are no different from energy transfers in, say, an electrical circuit. Let's take a closer look at how the laws of thermodynamics (physical rules of energy transfer) apply to living beings like yourself.

The First Law of Thermodynamics

The first law of thermodynamics thinks big: it deals with the total amount of energy in the universe, and in particular, it states that this total amount does not change. Put another way, the First Law of Thermodynamics states that energy cannot be created or destroyed. It can only change form or be transferred from one object to another.

This law may seem kind of abstract, but if we start to look at examples, we'll find that transfers and transformations of energy take place around us all the time. For example:

Light bulbs transform electrical energy into light energy (radiant energy).

One pool ball hits another, transferring kinetic energy and making the second ball move.

Plants convert the energy of sunlight (radiant energy) into chemical energy stored in organic molecules.

You are transforming chemical energy from your last snack into kinetic energy as you walk, breathe, and move your finger to scroll up and down this page.

Importantly, none of these transfers is completely efficient. Instead, in each scenario, some of the starting energy is released as thermal energy. When it's moving from one object to another, thermal energy is called by the more familiar name of heat. It's obvious that glowing light bulbs generate heat in addition to light, but moving pool balls do too (thanks to friction), as do the inefficient chemical energy transfers of plant and animal metabolism. To see why this heat generation is important, stay tuned for the Second Law of Thermodynamics.

The Second Law of Thermodynamics

At first glance, the first law of thermodynamics may seem like great news. If energy is never created or destroyed, that means that energy can just be recycled over and over again, right?

Well...yes and no. Energy cannot be created or destroyed, but it can change from more-useful forms into less-useful forms. As it turns out, in every real-world energy transfer or transformation, some amount of energy is converted to a form that's unusable (unavailable to do work). In most cases, this unusable energy takes the form of heat.

Although heat can in fact do work under the right circumstances, it can never be turned into other (work-performing) types of energy with 100% efficiency. So, every time an energy transfer happens, some amount of useful energy will move from the useful to the useless category.

Heat increases the randomness of the universe

If heat is not doing work, then what exactly does it do? Heat that doesn't do work goes towards increasing the randomness (disorder) of the universe. That may seem like a big logic jump, so let's take a step back and see how it can be the case.

When you have two objects (say, two blocks of the same metal) at different temperatures, your system is relatively organized: the molecules are partitioned by speed, with those in the cooler object moving slowly and those in the hotter object moving quickly. If heat flows from the hotter object into the cooler object (as it will spontaneously), the molecules of the hot object slow down, and the molecules of the cool object speed up, until all the molecules are moving at the same average speed. Now, rather than having a partition of between fast and slow molecules, we simply have one big pool of molecules going about the same speed - a less ordered situation than our starting point.

The system will tend to move towards this more disordered configuration simply because it's statistically much more likely than the temperature-separated configuration (i.e., there are many more possible states corresponding to the disordered configuration). You can explore this concept further in the videos in this tutorial, or in this straightforward physics video.

Entropy and the Second Law of Thermodynamics

The degree of randomness or disorder in a system is called its entropy. Since we know that every energy transfer results in the conversion of some energy to an unusable form (such as heat), and since heat that does not do work goes to increase the randomness of the universe, we can state a biology-relevant version of the Second Law of Thermodynamics: every energy transfer that takes place will increase the entropy of the universe and reduce the amount of usable energy available to do work (or, in the most extreme case, leave the overall entropy unchanged). In other words, any process, such as a chemical reaction or set of connected reactions, will proceed in a direction that increases the overall entropy of the universe.

To sum up, the First Law of Thermodynamics tells us about conservation of energy among processes, while the Second Law of Thermodynamics talks about the directionality of the processes, that is, from lower to higher entropy (in the universe overall).

Entropy in biological systems

One implication of the second law of thermodynamics is that in order for a process to happen, it must somehow increase the entropy of the universe. This may immediately raise some questions for you when you think about living organisms such as yourself. After all, aren't you a pretty ordered collection of matter? Every cell in your body has its own internal organization; the cells are organized into tissues, and the tissues into organs; and your entire body maintains a careful system of transport, exchange, and commerce that keeps you alive. Thus, at first glance, it may not be clear how you, or even a simple bacterium, can represent an increase in the entropy of the universe.

To clarify this, let's look at the energy exchanges that take place in your body - say, when you are going for a walk. As you contract the muscles of your legs to move your body forward, you are using chemical energy from complex molecules such as glucose and converting it into kinetic energy (and, if you're walking uphill, potential energy). However, you're doing this with pretty low efficiency: a large fraction of the energy from your fuel sources is simply transformed into heat. Some of the heat keeps your body warm, but much of it dissipates into the surrounding environment.

This transfer of heat increases the entropy of the surroundings, as does the fact that you're taking large, complex biomolecules and converting them into a lot of small, simple molecules, such as carbon dioxide and water, as you metabolize fuel to power your walk. This example uses a person in motion, but the same would be true for a person, or any other organism, at rest. The person or organism will maintain some basal rate of metabolic activity, causing the breakdown of complex molecules to smaller and more numerous ones and the release of heat, thus increasing the entropy of the surroundings.

Stated more generally, processes that locally decrease entropy, such as those that build and maintain the highly organized bodies of living things, can indeed take place. However, these local decreases in entropy can occur only with an expenditure of energy, where some of that energy is converted into heat or other non-usable forms. The net effect of the original process (local decrease in entropy) and the energy transfer (increase in entropy of surroundings) is an overall increase in the entropy of the universe.

To sum up, the high degree of organization of living things is maintained by a constant input of energy, and is offset by an increase in the entropy of the surroundings.

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The laws of thermodynamics (article) | Khan Academy

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